1. Field of the Invention
The present invention relates to a document information display system that displays a general view of the contents of a plurality of documents, a document information display method, and a document search method.
2. Description of the Background
With the widespread of computers and the Internet, rapid progresses have been made to put document information into electronic form. As available document information increases, it is an increasingly important issue to find out necessary information therefrom. Information search (retrieval) technologies are technologies to accomplish such issue, and recently it has been common to search for necessary information using a search engine that applies information search technologies.
In the case of major search engines available on the Internet, such as Google (http://www.google.com) or goo (http://www.goo.ne.jp), when a user inputs a search request, Web pages relevant to the request are retrieved through the Internet and search results are displayed in a list format according to an order of relevance degrees. Although the user can obtain necessary information for his or her, the search results may contain information irrelevant to the user's search request. However, when the search results are simply displayed in a list format, the user has to sort out and select necessary information by evaluating the contents of individual search results and this is laborious. Therefore, a mechanism for enabling a user to easily evaluate a group of the documents obtained as search results is needed.
One approach toward the above point is a technology to classify and display search results by using a clustering technology. Herein, the expression “clustering” means grouping of a group of documents in accordance with their similarity, and it is divided into two techniques: hierarchical clustering and non-hierarchical clustering. A result of hierarchical clustering has a tree structure and a result of non-hierarchical clustering has a flat structure wherein only grouping is carried out. As a clustering technique, for example, the method disclosed in JP Patent Publication (Unexamined Application) No. 9-62693, entitled “Document classifying method according to probability model.” WiseNut search (http://www.wisenut.com) adopted by Lycos search (http://www.lvcos.co.jp) classifies Web sites of search results and packs similar Web sites into a folder for display. On the other hand, Vivisimo (http://www.vivisimo.com) employs a hierarchical clustering technique for classifying and displaying search results in a tree structure. Both techniques do not simply enumerate search results in a list format, and they improve convenience for user's access to information by classifying search results in accordance with their contents.
However, when the classified results are displayed in a folder format, the contents of only one folder can be referred to at a time, thus resulting in the lack of the listing property on the whole document group. Further, even when a tree structure is employed for displaying the results, nodes of individual trees are required to be deployed and referred to in order, thus resulting in the lack of the listing property, just like displaying a folder format.